This is a question related to scheduling of the jobs i.e. the dependencies put in the scheduler related to execution of a particular job.
If JOB1 is taken as a reference and JOB2 is the successor job it means that the execution of JOB2 has a dependency on the execution of JOB1. Another way of putting it is JOB1 is predecessor to JOB2.
Example of triggered job can be a file-triggered job. Basically the scheduler will check whether the particular file has been created (as a result of successful execution of some other job) and then the specified job gets submitted.
I hope I am clear in my words. Corrections are welcome!!!!